1. Field of the Invention
The present invention relates to door securing devices, and more particularly to modifications thereto securing a door lock against unauthorized withdrawal.
2. Description of the Prior Art
With the recent increase in crime against property, various devices for securing doorways against unauthorized entry have appeared in the market. Of these, the after market modifications appears to be most attractive in view of the prevailing use by the public of standardized door locks. Typical of these after market modification kits are those shown in U.S. Pat. No. 3,318,123 wherein a plate is pivoted along the edge of the door to engage a groove in the latch bolt provided therefor. Alternatively replacement door lock assemblies have been provided, such as that shown in U.S. Pat. No. 2,593,573.
In the first instance, the disposition of the added mechanism on the edge of the door while suitable for its purpose, allows for unauthorized opening by the insertion of a thin tool like a screwdriver or credit card to lift this device off its engaging position. In the second instance the cost of purchasing the redundant structure of a modified door lock and the attendant necessity of discarding the original door lock assembly have militated against wide acceptance of the alternative device. Most other prior art devices fall generally into these two classes. For example, the device shown in U.S. Pat. No. 3,773,369 and the assembly shown in No. 3,095,724 each again illustrates the general approach to the problem in the market place.